The proposed longitudinal research project, in the context of an ecological/resource framework, attempts to understand the conditions under which the severely mentally ill and other homeless persons are able to secure and maintain stable housing (vs. remain homeless). Probability sampling methods will be used to obtain a representative sample of homeless adults in the Buffalo metropolitan area. A broad range of sites will be sampled, including psychiatric facilities, special programs for the homeless, food pantries, and the streets, in addition to the shelters and soup kitchens commonly included in past research on the homeless. Based on our framework, data will be collected in three domains: Personal Attributes, including psychiatric diagnoses and background characteristics; Resources, in personal, social, economic, and service areas; and Outcomes, including detailed information on the course of homelessness and on subsequent housing characteristics. The data will be obtained from four sources: the homeless participant; two significant others, including at least one family member; interviewer ratings; and agency records. The study is especially distinctive among existing studies on the homeless in considering a wide range of social resources, including social support, family social climate, and family violence as predictors of exiting homelessness and subsequent housing stability. The study also includes a longer follow-up period than has so far been attempted (five interviews over two years) and would allow a longitudinal comparison of a variety of important subgroups among the homeless, such as the severely mentally ill (defined based on DSM-III-R criteria for schizophrenia or major affective disorder), substance abusers (also defined based on DSM-III-R criteria), and homeless women (including those with children). The two principal research goals are to: (1) Determine factors associated with obtaining stable housing; and (2) Identify causal mechanisms involved in exiting homelessness. In addition, the study will: (a) provide information on the possible effectiveness of a full range of services currently used by the homeless and whether certain combinations of services may be particularly helpful; (b) compare the utility of several commonly used methods for assessing the mental health status of the homeless; and (c) develop new measures needed for the study of homelessness (e.g., to assess characteristics of homelessness and subsequent housing quality). Through extensive preliminary research, procedures have been refined to ensure a low attrition rate among the homeless sample in this longitudinal research.